Photovoltaic devices, such as amorphous silicon solar cells, are capable of converting solar radiation into useable electrical energy. The energy conversion occurs as a result of what is well known in the solar cell field as the photovoltaic effect. Solar radiation impinging on a solar cell and absorbed by the amorphous silicon generates electrons and holes. The electrons and holes are separated by a built-in electric field, for example, by a rectifying junction such as a Schottky barrier, in the solar cell. The electrons generated at the junction of a metal (Schottky barrier) and an N-type semiconductor body flow toward the semiconductor body where said electrons are collected. The separation of electrons and holes results in the generation of an electrical current.
Amorphous silicon Schottky barrier solar cells tend to generate higher currents but lower voltages than PIN amorphous silicon solar cells. Application Ser. No. 901,256, filed Apr. 28, 1978, and incorporated herein by reference, discloses a Schottky barrier amorphous silicon solar cell incorporating a thin highly doped P.sup.+ layer contiguous to the high work function Schottky barrier metal. Application Ser. No. 819,936, filed July 28, 1977, now U.S. Pat. No. 4,117,506, and incorporated herein by reference, discloses an amorphous silicon solar cell incorporating a thin insulating region between the body of amorphous silicon and the high work function Schottky barrier metal. Solar cells incorporating either the thin highly doped P.sup.+ layer or the thin insulating region exhibit higher open circuit voltages than conventional high work function metal-amorphous silicon Schottky barrier solar cells. Since the magnitude of the open circuit voltage of the solar cell is dependent, inter alia, upon the height of the barrier between the body of amorphous silicon and the Schottky barrier metal, it would be desirable to increase the barrier height and increase the open circuit voltage without decreasing other parameters of the solar cell such as the short circuit current.